[ECOS] RE: memory alignment issue when compile eCos with codesourcery toolchain arm-none-eabi-gcc

["Lu Karl-B01968" <Karl dot Lu at FREESCALE dot COM>]

Thanks Chris. 
We are using Freescale i.Mx31 which is an ARM11 chip. 
The problem happens when a 2-byte aligned address is assigned to pointer which requires 4-byte aligned. For example, in lan92xx_send() in if_lan92xx.c, one code line is as below,
----------
       unsigned int data, *pdata;
       pdata = (unsigned int *)sg_list[i].buf;
-----------
Here sg_list[i].buf is 2-byte aligned while pdata needs 4-byte aligned. Then following code will hang the system
----------
       data = *pdata;	
---------
In fconfig.c, the problem is similar. Val_ptr is of "void *" type and it is pointed to a char in a long string (for command processing). It is not guaranteed to be 4-byte aligned. Then when setting IP address, following code will fail
----------
        lp += diag_sprintf(lp, "%s", inet_ntoa((in_addr_t *)val_ptr));
---------
Because (in_addr_t *) in function inet_ntoa expects val_ptr to be 4-byte aligned.

Do you think there is a way to work around this issue without code modification?

Regards
Karl Lu

-----Original Message-----
From: Chris Zimman [mailto:czimman@bloomberg.com] 
Sent: 2008å10æ15æ 19:16
To: Lu Karl-B01968
Cc: ecos-discuss-owner@ecos.sourceware.org
Subject: RE: memory alignment issue when compile eCos with codesourcery toolchain arm-none-eabi-gcc

> We are using arm-none-eabi toolchain (we downloaded 2008q1 release 
> from
CodeSoucery website) to build eCos/redboot. Thanks to Chris, we resolved the
> link issues in arm.ld but we are meeting memory alignment issue now. 
> In
ecos/package/redboot/current/include/net/net.h, we have to modify the code,
> addÂ__attribute__((aligned(4),packed)) for struct eth_header_t and 
> pktbuf_t
and force them to the 4-byte aligned. Otherwise, Ethernet driver code
> will hang the system during RedBoot startup. We also find in
ecos/package/redboot/current/src/fconfig.c, we also have to force val_ptr in
> get_config() to be 4-byte aligned otherwise we can't config IP address 
> when
we run fconfig in redboot. This command will abort and report "**
> command abort - illegal memory access?" 
> We can modify the code manually whenever we meet such kind of memory
alignment problem but it is really annoying. We wanted to find a compile option > in arm-none-eabi-gcc to work around this issue but failed. Did you meet the similar memory alignment issue? How did you work around this issue?

Hi Karl,

I didn't run into any alignment issues per se.  Without knowing anything else, where is val_ptr pointed at?  Is the pointer valid and pointing to what it should be?  I would suspect something other than the EABI related stuff directly.

Which ARM processor are you targeting?
 
Just for the sake of comparison, I'm attaching the linker script that I use for EABI.  Have a look at that and let's go from there.  

--Chris